Zinc alloy negative electrode and preparation method and application thereof

Abstract

The application discloses a zinc alloy negative electrode and a preparation method and application thereof, and relates to the following steps: mixing zinc salt, nickel salt and water to obtain an electroplating solution; under a constant current mode, the electroplating solution is subjected to two-step electrodeposition on the surface of a base material to obtain the zinc alloy negative electrode; in the first-step electrodeposition process, the molar ratio of the zinc salt to the nickel salt in the electroplating solution is 50-150:1; and in the second-step electrodeposition process, the molar ratio of the zinc salt to the nickel salt in the electroplating solution is 10-30:1. The zinc-nickel alloy with gradient grain size can be obtained by regulating the alloy components, the alloy has an ordered and continuous gradient grain boundary network, and the alloy is used as a reaction surface of a water-based zinc metal battery and has excellent high-rate electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc metal battery technology, specifically relating to a zinc alloy negative electrode, its preparation method, and its application. Background Technology

[0002] The deposition / stripping process of zinc anodes is essentially a hostless reaction, and its reversibility is highly dependent on the interfacial environment and structural evolution. Under high-rate conditions, rapidly migrating zinc ions preferentially deposit at local active sites, leading to heterogeneous nucleation and the formation of a loose, porous deposition layer. Especially under high current density and high areal capacity conditions, the constrained kinetics easily lead to stress concentration, which in turn causes zinc foil cracking and pulverization. At the same time, unavoidable hydrogen evolution and corrosion side reactions at interfacial defects further reduce coulombic efficiency and accelerate electrode failure. Therefore, achieving uniform zinc deposition and maintaining a stable anode structure under harsh operating conditions is a key challenge for promoting the practical application of aqueous zinc metal batteries.

[0003] Currently, artificial protective layers can alleviate interfacial side reactions to some extent, but their limited mechanical adjustment capabilities cannot fundamentally solve the problem of insufficient main body support in zinc anodes, and structural instability is still prone to occur during long-term cycling. Alloying strategies provide an effective way to improve deposition behavior by adjusting the zinc matrix structure, but traditional alloys are difficult to adapt to the continuously changing interfacial environment at high rates and high capacities, and local ion enrichment and stress concentration can still induce uneven deposition and crack propagation. Summary of the Invention

[0004] To address the problems of side reactions and stress concentration-induced structural failure in zinc anodes during high-rate and high-capacity cycling in existing technologies, this invention provides a zinc alloy anode, its preparation method, and its application. By controlling the alloy composition, a zinc-nickel alloy with gradient grain size can be obtained. This alloy has an ordered and continuous gradient grain boundary network, which can be used as the reaction surface of an aqueous zinc metal battery, exhibiting excellent high-rate electrochemical performance.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: A method for preparing a zinc alloy negative electrode involves mixing zinc salt, nickel salt, and water to obtain an electroplating solution; under constant current mode, the electroplating solution is electrodeposited onto the surface of a substrate in two steps to obtain a zinc alloy negative electrode. In the first step of electrodeposition, the molar ratio of zinc salt to nickel salt in the electroplating solution is 50~150:1; In the second step of electrodeposition, the molar ratio of zinc salt to nickel salt in the electroplating solution is 10~30:1.

[0006] Preferably, the zinc salt is ZnSO4·7H2O, ZnCl2 or Zn(CF3SO3)2, and the nickel salt is NiSO4·6H2O or NiCl2; during the two-step electrodeposition process, the concentration of zinc salt in the electroplating solution is 0.5~1.5 mol / L.

[0007] Preferably, the substrate is copper foil, titanium foil, or carbon-based material.

[0008] Preferably, the current density of the electrodeposition is 5~30 mA / cm². 2 Further preferably, it is 10~20 mA / cm 2 .

[0009] The inventors unexpectedly discovered that a zinc-nickel alloy anode with a gradient grain size from the surface to the interior can be constructed through a two-step electrodeposition process using electroplating solutions of different concentrations. The grain size gradually increases from the surface to the bottom, thus building an ordered and continuous gradient grain boundary network within the electrode. The fine grains on the surface provide abundant nucleation sites, promoting the orderly deposition of zinc at the interface. Simultaneously, during high-rate and high-capacity cycling, the stress generated by rapid interfacial reactions and volume changes can be smoothly transmitted from the surface to the interior of the electrode along the gradient grain boundary network, preventing stress from continuously accumulating within the grains or at local interfaces. This effectively inhibits crack initiation and propagation, reduces anode breakage and pulverization, and maintains the integrity of the electrode structure and reaction interface. This zinc-nickel alloy anode exhibits excellent cycling stability under high-rate and high-area-capacity conditions.

[0010] The present invention also provides a zinc alloy negative electrode prepared by the above preparation method, wherein the grain size exhibits a gradient distribution that increases from the surface layer to the bottom layer.

[0011] This invention also provides an application of the above-mentioned zinc alloy negative electrode, which is used to prepare aqueous zinc metal batteries.

[0012] The advantages of this invention are: This invention constructs a zinc-nickel alloy anode with a gradient grain size through a two-step electrodeposition process. The grain size gradually increases from the surface to the bottom, thereby creating an ordered and continuous gradient grain boundary network within the electrode. The fine surface grains provide abundant nucleation sites, promoting uniform zinc deposition; the gradient grain boundary network guides the smooth transfer and dispersion of stress generated during cycling into the electrode interior, inhibiting crack initiation and propagation, thus improving the structural and cycling stability of the anode under high rate and high capacity conditions. Attached Figure Description

[0013] Figure 1 XRD pattern (a) of Zn|Ni-1 in Example 1; surface scan (b) of Zn|Ni-1 in Example 1.

[0014] Figure 2 The images show the cross-sectional electron backscatter diffraction inverse pole figures of Zn|Ni-1 before (a) and after (b) cycling in Example 1, along with the corresponding nuclear average orientation difference (KAM) plots and their fitted frequency distributions.

[0015] Figure 3 The inverse pole figures of cross-sectional electron backscatter diffraction diffraction for Zn|Ni-2 before (a) and after (b) cycling in Comparative Example 1 are shown, along with the corresponding nuclear average orientation difference (KAM) plots and their fitted frequency distributions.

[0016] Figure 4 This is a comparison chart of the zinc / zinc symmetric battery cycle performance of Zn|Ni-1 in Example 1, Zn|Ni-2 in Comparative Example 1, Zn|Ni-3 in Comparative Example 2, and Bare Zn in Comparative Example 3.

[0017] Figure 5 The graph shows a comparison of the electrochemical performance of Zn|Ni-1 in Example 1, Zn|Ni-2 in Comparative Example 1, Zn|Ni-3 in Comparative Example 2, and Bare Zn in Comparative Example 3 using ammonium vanadate cathode. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments. The raw materials described in the present invention are all obtained through commercial means. Unless otherwise specified, the preparation methods described in the present invention are conventional preparation methods in the art. The following embodiments are intended to illustrate the present invention and not to further limit the present invention.

[0019] Example 1 A method for preparing a gradient zinc-nickel binary alloy anode by electrodeposition on a copper substrate includes the following steps: Step 1: Weigh 28.756 g of zinc sulfate heptahydrate ZnSO4·7H2O and 0.26285 g of nickel sulfate hexahydrate NiSO4·6H2O, add them to 100 ml of deionized water, stir and dissolve at room temperature to obtain the first electroplating solution; Step 2: Weigh 28.756 g of zinc sulfate heptahydrate ZnSO4·7H2O and 1.31425 g of nickel sulfate hexahydrate NiSO4·6H2O, add them to 100 ml of deionized water, stir and dissolve at room temperature to obtain the second electroplating solution; Step 3: Cut the initial copper foil and zinc foil to obtain copper and zinc sheets of fixed size that can be put into the electrolytic cell. Then, perform surface treatment on the copper and zinc sheets, remove any dust, oil, oxides, etc. that may be present with alcohol, and place them in the plating tank after rinsing with deionized water. Step 4: Select a constant current of 20 mA / cm 2 The electroplating time is 30 min, and the electrodeposition process is carried out using the first electroplating solution; Step 5: After electrodeposition is complete, remove the positive electrode deposition side, rinse with deionized water, dry in a drying oven, and then remove. Step 6: Select a constant current of 20 mA / cm 2 The electroplating time is 30 min, and the electrodeposition process is carried out on the basis of the deposition layer obtained in step 5 using the second electroplating solution; Step 4: After electrodeposition, remove the positive electrode deposition side, rinse with deionized water, dry in a drying oven, and then remove to obtain Zn|Ni-1 with a deposition areal capacity of 20 mA h / cm². 2 ; Step 5: Using a tablet press, the electroplated layer, along with the copper substrate, is punched into a 15 mm diameter disc for use as the negative electrode of the zinc-ion battery, where the deposited layer serves as the reaction surface of the battery.

[0020] Comparative Example 1 A method for preparing a zinc metal anode by electrodeposition on a copper substrate includes the following steps: Step 1: Weigh 28.756 g of zinc sulfate heptahydrate ZnSO4·7H2O and 1.31425 g of nickel sulfate hexahydrate NiSO4·6H2O, add them to 100 ml of deionized water, stir and dissolve at room temperature to obtain the electroplating solution; Step 2: Cut the initial copper foil and zinc foil to obtain copper and zinc sheets of fixed size that can be put into the electrolytic cell. Then, perform surface treatment on the copper and zinc sheets, remove any dust, oil, oxides, etc. that may be present with alcohol, and place them in the plating tank after rinsing with deionized water. Step 3: Select a constant current of 20 mA / cm 2 The electroplating time is 60 min, and the electrodeposition process is carried out. Step 4: After electrodeposition, remove the positive electrode deposition side, rinse with deionized water, dry in a drying oven, and then remove to obtain Zn|Ni-2 with a deposition areal capacity of 20 mA h / cm². 2 ; Step 5: Using a tablet press, the electroplated layer, along with the copper substrate, is punched into a 15 mm diameter disc for use as the negative electrode of the zinc-ion battery, where the deposited layer serves as the reaction surface of the battery.

[0021] Comparative Example 2 A method for preparing a zinc metal anode by electrodeposition on a copper substrate includes the following steps: Step 1: Weigh 28.756 g of zinc sulfate heptahydrate ZnSO4·7H2O and 0.26285 g of nickel sulfate hexahydrate NiSO4·6H2O, add them to 100 ml of deionized water, stir and dissolve at room temperature to obtain the electroplating solution; Step 2: Cut the initial copper foil and zinc foil to obtain copper and zinc sheets of fixed size that can be put into the electrolytic cell. Then, perform surface treatment on the copper and zinc sheets, remove any dust, oil, oxides, etc. that may be present with alcohol, and place them in the plating tank after rinsing with deionized water. Step 3: Select a constant current of 20 mA / cm 2 The electroplating time is 60 min, and the electrodeposition process is carried out. Step 4: After electrodeposition, remove the positive electrode deposition side, rinse with deionized water, dry in a drying oven, and then remove to obtain Zn|Ni-3 with a deposition areal capacity of 20 mA h / cm². 2 ; Step 5: Using a tablet press, the electroplated layer, along with the copper substrate, is punched into a 15 mm diameter disc for use as the negative electrode of the zinc-ion battery, where the deposited layer serves as the reaction surface of the battery.

[0022] Comparative Example 3 Ordinary zinc sheets (Bare Zn) with a thickness of 50 micrometers were used. The zinc sheets were purchased from Weifang Purun Co., Ltd., with a zinc content of over 99.9% and a sheet areal capacity of approximately 29 mA h / cm². 2 A tablet press is used to punch out 15 mm diameter discs for use as the negative electrode in zinc-ion batteries.

[0023] like Figure 1 As shown, (a) is the XRD pattern of Example 1 (Zn|Ni-1), and (b) is the scan image of Example 1 (Zn|Ni-1). The results show that the obtained deposited layer is a zinc-nickel alloy and has a distinct and uniform hexagonal lamellar structure.

[0024] like Figure 2 As shown, the electron backscatter diffraction inverse pole figure and corresponding nuclear average orientation difference (KAM) of Example 1 (Zn|Ni-1) are presented, visually revealing the regular grain size gradient distribution of Example 1 (Zn|Ni-1). The initial KAM value of Example 1 (Zn|Ni-1) is 0.30, and the KAM value only increases to 0.35 after cycling. Simultaneously, the stress distribution diagram shows that stress can be smoothly transmitted downwards along the grain boundary network to the bottom region, maintaining a low stress state within the grains. This ordered grain boundary network fundamentally inhibits crack initiation and propagation, thereby ensuring the cycling stability of the negative electrode.

[0025] like Figure 3As shown, the electron backscatter diffraction inverse pole figure and corresponding nuclear average orientation difference of Comparative Example 1 (Zn|Ni-2) are presented, intuitively revealing the irregular grain size distribution of Comparative Example 1 (Zn|Ni-2). Although the initial KAM value of Comparative Example 1 (Zn|Ni-2) is 0.28, the KAM value increases significantly to 0.57 after cycling. Simultaneously, the stress distribution diagram shows that high local strain regions are widely distributed within the grains. This significant stress concentration directly leads to grain deformation and crack propagation, and exposes highly active sites, thereby promoting side reactions such as hydrogen evolution.

[0026] like Figure 4 The figure shows the cycle performance of zinc-symmetric batteries in Example 1 (Zn|Ni-1), Comparative Example 1 (Zn|Ni-2), Comparative Example 2 (Zn|Ni-3), and Comparative Example 3 (Bare Zn). In Example 1, the cycle performance was achieved at a high current density of 5 mA cm⁻¹. –2 Under the conditions of 10% negative electrode utilization, the symmetrical cell assembled in Example 1 (Zn|Ni-1) exhibited a lower initial hysteresis voltage and could cycle stably for 3500 h. The symmetrical cell assembled with the negative electrode of Comparative Example 1 (Zn|Ni-2), while maintaining some stability initially, failed after 500 h due to increased polarization voltage. In Comparative Example 2 (Zn|Ni-3), the hysteresis voltage increased significantly with increasing cycle time. The Zn|Ni-3 symmetrical cell failed after 400 h. Comparative Example 3 (Bare Zn) only cycled stably for 100 h before short-circuiting. The symmetrical cells verified the advantages of the zinc-nickel alloy of this invention in terms of high rate and high capacity: its gradient structure promotes interfacial dynamics compensation, reduces the nucleation barrier of zinc, and accelerates interfacial charge transfer; simultaneously, the ordered, continuous gradient grain boundary network facilitates the transmission and dispersion of cyclic stress, thereby maintaining the stability of the electrode structure and interface. The symmetric cell with Zn|Ni-1 alloy as electrode maintained a stable voltage curve throughout the cycling process at 10% discharge depth, without significant polarization increase, indicating that the gradient structure has excellent interfacial reversibility and long-term cycling stability.

[0027] like Figure 5 The figures shown are full-cell performance graphs for Example 1 (Zn|Ni-1), Comparative Example 1 (Zn|Ni-2), Comparative Example 2 (Zn|Ni-3), and Comparative Example 3 (Bare Zn). The full cells used ammonium vanadate as the positive electrode active material, glass fiber as the separator, and zinc sulfate aqueous solution as the electrolyte to assemble into button cells. Regarding long-cycle stability, even at a current density of 1 A / g and a high positive electrode load (20 mg / cm³), [the cells showed good performance]. 2Under the harsh conditions of [specific conditions - likely referring to specific conditions or parameters], the full cell with the matched deposited Zn|Ni-1 alloy can still cycle stably for nearly 1000 cycles. However, when using Comparative Example 3 (Bare Zn), the full cell only cycled 100 times before its capacity rapidly decayed. The excellent long-term cycling stability can be attributed to the stable interface on the negative electrode side of the gradient alloy. In contrast, bare zinc exhibits uncontrolled zinc deposition / stripping, increasing interfacial impedance and leading to cell capacity decay.

Claims

1. A method for preparing a zinc alloy negative electrode, characterized in that: Zinc salt, nickel salt and water are mixed to obtain an electroplating solution; under constant current mode, the electroplating solution is used to obtain a zinc alloy negative electrode on the substrate surface through two-step electrodeposition. In the first step of electrodeposition, the molar ratio of zinc salt to nickel salt in the electroplating solution is 50~150:1; In the second step of electrodeposition, the molar ratio of zinc salt to nickel salt in the electroplating solution is 10~30:

1.

2. The preparation method according to claim 1, characterized in that: The zinc salt is ZnSO4·7H2O, ZnCl2, or Zn(CF3SO3)2, and the nickel salt is NiSO4·6H2O or NiCl2; during the two-step electrodeposition process, the concentration of zinc salt in the electroplating solution is 0.5~1.5 mol / L.

3. The preparation method according to claim 1, characterized in that: The substrate is copper foil, titanium foil, or carbon-based material.

4. The preparation method according to claim 1, characterized in that: The current density of the electrodeposition is 5~30 mA / cm². 2 .

5. The preparation method according to claim 4, characterized in that: The current density of the electrodeposition is 10~20 mA / cm². 2 .

6. The zinc alloy negative electrode prepared by the preparation method according to any one of claims 1-5, characterized in that: In the zinc alloy negative electrode, the grain size exhibits a gradient distribution that increases from the surface layer to the bottom layer.

7. The application of the zinc alloy negative electrode according to claim 6, characterized in that: It was used to prepare aqueous zinc metal batteries.

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